Tapered gap means for magnetic translating device



March 2, 1965 G. c. TIBBETTS TAPERED GAP MEANS FOR MAGNETIC TRANSLATINGDEVICE Filed July 6, 1962 INVENTOR. 6622 06 6. jijzzf M W United StatesPatent Maine Filed July 6, 1962, Ser. No. 208,077 13 Claims. (Cl.317-173) The present invention rel-ates to magnetic translating deviceshaving a movable armature and capable of translating mechanical toelectrical energy or vice versa due to the operation of variable gapsand variable magnetic fluxes, and more particularly relates to theorientation of the surfaces defining the gaps relative to the armaturefree end.

It is an object of this invention to provide optimum stability of thearmature for all deflections of the armature of a magnetic translatingdevice.

It is another object of this invention to provide means creating amagnetic field comprising gap-defining pole faces at angles relative tothe opposing faces of the armature passing therebetween.

More particularly it is an object of this invention to orient thesurfaces, forming the pole faces of the means creating the magneticfield at a vibratory portion of the armature, and the opposing faces ofthe armature at angles relative to each other such that the planes, inwhich the pole face surfaces lie, intersect the corresponding planes, inwhich the opposing faces of the armature lie, in lines whichsubstantially define a plane such 1 that the virtual pivot axis of thearmature lies substantially in the plane so defined. The latter plane issubstantially perpendicular to the others, for very small gap angles.Insofar as the portion of the armature between the pole facesapproximates a rigid body, the virtual pivot axis is so defined thatsaid portion moves, under the action of magnetic forces, as if rigidlypivoted about said axis.

These and further objects will be apparent from the followingdescription and drawings in which:

FIGURE 1 shows the general configuration of the invention;

FIGURE 2 is a view in section showing the invention utilized in amagnetic translating device;

FIGURE 3 is an enlarged view in perspective of the tapered pole pieces;

FIGURE 4 is an end view along line 44 of FIGURE 2 showing the taperedpole pieces defining the tapered gaps between the pole faces and thearmature; and

FIGURES 5 and 6 show modified embodiments of the invention.

In its broad embodiment the present invention comprises means fordefining a tapered gap relative to an armature so that with largedeflections of the armature there will be optimum stability throughoutthe deflection. Thus the means may take the form of a pole pieceinclined relative to the armature to create the tapered gap as showngenerally in FIGURE 1 with pole piece 1 having pole face 2 at an angleto the armature 3; or may comprise a pole piece whose constant thicknessextends parallel to the normal plane of the armature outside theprojected area of the armature, but is recessed at a tapered anglerelative to the armature in the projected area as shown in FIGURES 2 and3. By choosing the angles as hereinbefore described, the gap closes oropens substantially sector-wise under the combined action of magneticand external forces, the relative flux distribution in the gap remainssubstantially unchanged, and thereby the effective point of applicationof the magnetic forces remans substantially stationary relative to thearmature, resulting in optimum "ice stability of the armature for alldeflections. Closing sector-wise as used throughout the specificationand claims shall be understood to mean that the closing surfaces form anangle whose apex does not move substantially as the surfaces closewhereby the facing surfaces of the armature and poles reach substantialparallelism just as they touch.

The invention has application to the broad magnetic translating deviceof FIGURE 1 utilizing an armature 3 having some portion such as its endfixed relative to a base 4. In particular, the invention may be employedin electromagnetic transducers such as hearing aid microphones orreceivers, and FIGURE 2 shows the invention utilized in the translatingdevice 5 of copending application Serial No. 168,183, filed January 23,1962. In that figure the pole pieces have end portions of constantthickness and parallel to the plane of the armature when centered, buthave their central portions recessed to provide a taper relative to thearmature. The armature 6 of the translating device is suspended at itsuppermost end 7. In this case the virtual pivot axis is intermediate theupper and lower portions of the folded armature in a direction parallelto line 44, and is intermediate the pole pieces 1 and the folded portion9 of the armature in a perpendicular direction. FIGURE 3 shows themagnets 8 of the translating device which extend laterally of the planeof the armature free end and have pole pieces 1 on their surfacesadjacent the armature, with the surfaces of the pole pieces being offsetat a tapered angle as shown. FIGURE 4 is a further view of such polepieces to indicate the relationship between the armature and the polefaces.

FIGURE 5 shows a modified configuration wherein the tapered gaps areformed by pole pieces llh-aving their pole faces adjacent the armatureparallel to each other, with armature 12 having a tapered end to providesurfaces 13 defining the tapered gaps with the pole faces. Suchconfiguration is the reverse of FIGURE 1. It is readily apparent that aconfiguration intermediate the extremes of FIGURES l and 5, having thepole faces non-parallel as in'FIGURE 1 and the armature end. surfacesnon-parallel as in FIGURE 5, would also be effective as long as theangles were chosen as hereinbefore described.

FIGURE 6 depicts a further embodiment of the invention wherein the polefaces 14 are presented directly by the surfaces of the magnets 15, withno intermediate pole pieces. Since the flux-collecting and fluxdistribut ing functions of the pole pieces are omitted, the magnetspreferably are tapered in the same sense as the gaps or otherwiseprocessed so that they are elfectively thinner at their edges nearestthe virtual pivot axis and progressively effectively thicker towardtheir edges away from said axis. For example, by having the taper of themagnet such that the ratio of magnet thickness to gap thickness remainssubstantially constant from point to point in the direction of theextent of the armature at center rest position, the relative fluxdistribution in the gap again remains substantially unchanged as thefree end of the armature moves substantially sector-wise to- Ward oraway from either magnet. It is apparent that the tapered gaps could bedefined by similar tapered magnets whose adjacent gap-defining surfacesare parallel to each other but utilized with a tapered armature as inFIGURE 5, or any intermediate configuration with nonparallel magnets andarmature surfaces as described above concerning FIGURE 5.

The drawings are exaggerated, and not intended to limit the invention toconfigurations having gaps with tapers as large as depicted.

Many modifications will be apparent to the artisan. It is obvious thatthe invention in its broadest aspects can n a magnetic translatingdevice' including an armatur having a substantially rig'idly 'fi'riedportion and a vibratory portion, the improvement *comprising'means,efini'ng at' least one tapered gapbetween'thearmature sa'idtranslating-*dvice -a'ndmeans supplyinga mag n'etic field' irr theviciriity of a vibratoryregion of the armaturej-f closable substantiallysectorwise, anddefining a substantially invariant-relative'fiuXdistribution in said 'gap throughout deflections ot-"the armature, thefirst -"i1arr1'ed means comprising surfaces lying in respective planesintersecting in aline substantially fixed relative to arrdsp'aac'ed'from th fixed portion of the armature.

21 The improvement as recited inclaim l wherein' the first-nained'meanscomprise the surfacesofthe armature anathema-named means. I I

3. 1he improvement as recited in claim 1 wherein the rsenamed meanscomprisesat least-one surface of the ast-named-means. I 4.The-improvement recited in' claim 3 wherein the Y lastmar'nedmeans'comprisesat least one magnet.

5. "Theimprovement as recited-in claim4 wherein said -n1agnetistapered=in the samesense as said gap.

' 6. '.l" he im' pavement as recited -in claim" 3 wherein eiid at leastne surface is at an angle-relative to'- the he improvement-as*recited inclaim 6 whe'rein the" 's rfac? of the armature i adjacent said at--leastone surface is also at an angle "relative'=to* the-general extent thefirst-named means comprises at least one pole piece forming'part ofsaidlast-named means.

11. In a magnetic translating device including an armature having asubstantially rigidly fixed portion and a vibratory portion, theimprovement comprising means, including a vibratory region of thearmature and a pole face presented thereto, defining a tapered gaptherebetween, closable substantially sectorwise,-and defining asubstantially invariant relative flux distribution in the gap throughoutdeflections of the armature, the plane in which lies the pole face andthe plane in which lies the adjacent surface of said vibratory region ofthe armature intersecting in a line substantially fixed relative to andspaced from the fixed portion of the armature.

' 12. The improvement as recited in claim 11' including asecond means onthe side of 'the'arm-ature opposite the first said means, and similarlyincluding a pole face presented to the armature symmetrical with respectto the first-named pole face. a

13. In a magnetic translating device including'an armature having asubstantially rigidly fixed portion and a vibratory portion; theimprovement comprising magnets extending on opposite sides of thearmature and presenting pole faces to a vibratory region of the armaturesuch that theplanes inWhichlie' the pole faces and the planes in whichBethe-respective adjacent surfaces of said vibratory region of thearmature respectively intersect References Cited by the Examiner UNITEDSTATES PATENTS 1,568,589 1 /26 Eddington 317-173 2,718,614 -9/s5 Gamble317-171 2,754,685 7/56 Lansky '317171 2,941,130 6/60 Fischer 317-471'FOREIGN PATENTS 1,052,458 37-59 Germany.

112,593 12/44 'Sweden.

LARAMIE E; ASKIN, Primary Examiner. E. JAMES SAX ,"JOHN F."BURNS,Examiners.

1. IN A MAGNETIC TRANSLATING DEVICE INCLUDING A ARMATURE HAVING ASUBSTANTIALLY RIGIDLY FIXED PORTION AND A VIBRATORY PORTION, THEIMPROVEMENT COMPRISING MEANS, DEFINING AT LEAST ONE TAPERED GAP BETWEENTHE ARMATURE OF SAID TRANSLATING DEVICE AND MEANS SUPPLYING A MAGNETICFIELD IN THE VICINITY OF A VIBRATORY REGION OF THE ARMATURE, CLOSABLESUBSTANTIALLY SECTORWISE, AND DEFINING A SUBSTANTIALLY INVARIANTRELATIVE FLUX DISTRIBUTION IN SAID GAP THROUGHOUT DEFLECTIONS OF THEARMATURE, THE FIRSTNAMED MEANS COMPRISING SURFACES LYING IN RESPECTIVEPLANES INTERSECTING IN A LINE SUBSTANTIALLY FIXED RELATIVE TO AND SPACEDFROM THE FIXED PORTION OF THE ARMATURE.